We pressed Brewster for more details, but they would only give us this statement:

"We take privacy extremely seriously at Brewster. When we launched yesterday, we had a tremendous number of user signups, and fixed a number of problems, including scale issues and bugs.

One unfortunate problem that arose was for Foursquare users who were fans, but not friends, of other Foursquare users. Even further, Foursquare only offers the ability to be fanned to an extremely small number of users. In this case, if we had the contact information from a full Foursquare friend, we briefly displayed their contact information to fans. This happened with one user who was fans of multiple people on Foursquare.

As soon as we heard of this issue from the user, we made sure this bug was resolved immediately, and put safeguards in place to ensure it never happens again. This is the only instance we heard of this issue.

Separately, from this bug, we have also responded to questions from users related to information that they had access to from different services. For instance, a user might have a public photo available that they haven't seen before, or a phone number rightfully accessible if connected on Foursquare. These instances are completely consistent with the access the user gives these third-party services.

Brewster strives to be a trusted personalized address book for our users. We hope this serves as an example of how seriously we take issues of privacy, how candid we will be if issues ever arise, and that our users remain a top priority.